The present invention relates to a toner cleaning apparatus for use in an electrophotographic apparatus which comprises an electrostatic charge retentive member movably arranged in a given direction, means for forming an electrostatic charge latent image corresponding to an image of a document to be duplicated, means for developing the latent image with a dry toner to form a toner image and means for transferring the toner image onto a record paper, said latent image forming means, developing means and transferring means being arranged in this order viewed in the moving direction of the charge retentive member.
In the electrophotographic apparatus of the kind mentioned above, residual toner on the charge retentive member has to be removed or cleaned after the transferring operation. Two cleaning methods have been known and practiced. In one method use is made of an exclusive cleaning device and in the other method the developing device for effecting the toner development is utilized also for cleaning the residual toner. In the first method it is possible to effect the cleaning step independently from the developing step and thus the whole duplicating steps can be carried out in a very efficient manner, but the removed toner could not be used again for the development and thus is wasted. In order to avoid such a drawback it is necessary to provide a very complicated and large mechanism for transporting the removed toner at the cleaning section to the toner developing device. Whereas in the second method the removed toner naturally enters into the developing device and is used again for development, but in this case the toner developing step and cleaning step could not be effected independently from each other and thus the whole duplicating steps might be inefficient.
The exclusive cleaning device may be constructed in various forms, but all of them have a serious drawback that maintenance is very cumbersome. In U.S. Pat. Nos. 2,832,977 and 2,911,330 the cleaning device is formed as a cleaning brush which is rotated at a high speed with being in contact with the charge retentive member so as to brush the residual toner off the charge retentive member. The removed toner particles are collected by a filter with the aid of a vacuum suction device. Such a cleaning device has a disadvantage that during the long time operation the cleaning brush might be deformed to decrease a cleaning efficiency and the filter might be filled with toner particles to decrease a toner collection efficiency. Therefore the toner particles brushed off the retentive member might scatter and float inside the apparatus. A web type cleaning device is also known in which an elongated web is pressed against the charge retentive member by a resilient roller to wipe the residual toner off the retentive member. The web is installed in the apparatus as a roll and is gradually taken-up by a roller. But since the web has a finite length the web roll must be exchanged. Further, since the web is resiliently urged against the charge retentive member the surface of member is liable to be injured. There has been further known a blade type cleaning device in which a blade made of resilient material such as rubber is urged against the charge retentive member so as to wipe the residual toner off the member. In such a device the blade is liable to wear relatively soon and should be exchanged frequently. In the U.S. Pat. No. 2,911,330 there is described a cleaning device which utilizes a magnetic force. For instance, in case of using a two component developer such as a combination of magnetic carriers and toner particles or beads and toner particles, the carriers of magnetic particles or beads serve to attract the residual toner on the charge retentive member by means of a magnet roller or bucket conveyor. During the cleaning operation a bias voltage may be applied or a separate discharging member may be provided in order to improve the cleaning effeiciency. However in such a device the carriers have to be exchanged periodically, because the toner retaining ability of carriers decreases owing to toner particles adhered to the carriers.
As explained above various types of the exclusive cleaning devices have been developed, but have a common drawback that the periodic maintenance is required. That is to say every several to ten thousand copies cleaning brush, web, blade or filter should be exchanged.